Modern mobile stations, sometimes referred to as mobile terminals or user equipment (UE), are often capable of connecting to and communicating with two or more different types of radio access networks. One example is a dual-mode mobile terminal capable of connecting to a second generation (2G) radio access network, such as the Global System for a Mobile communication (GSM), Digital Advanced Mobile Phone System (D-AMPS), or Pacific Digital Cellular system (PDC), as well as to a third generation (3G) radio access network, such as Universal Mobile Telecommunication System (UMTS), Terrestrial Radio Access Network (UTRAN). Other radio technologies, such as Bluetooth or 802.11, may also be used. An environment that enables access to more than one radio access technology (RAT) is called a multi-access environment.
In general, when the mobile station is “attached” to a network, it can be in either an idle state in which it is not involved in an active connection, e.g. a communication with another subscriber or content server, or in an connected mode in which the mobile terminal is engaged in active connection, e.g., communicating with another subscriber or content server, and receiving service from the network. Although the states of the mobile station may have different labels in different systems, the term “idle” mobile station is used to cover a mobile station in any state in which the mobile station is powered-on but is not actively participating in a communication. During an idle state, the mobile station may select, register with, and “camp on” a cell, belonging to a certain RAT, in order to obtain service when desired by the mobile subscriber or when an incoming call is made to the mobile subscriber. Non-limiting examples of a mobile station being in an idle state where it selects the service area to receive service includes an GSM idle state, a GPRS MM ready state, a GPRS MM stand by state, a CELL_FACH state, a CELL_PCH state, and a URA_PCH state.
In cellular systems, a mobile stations in idle mode autonomously performs a cell-reselection procedure in which the mobile station reads system information (all or only part) broadcast by various cells, including the cell in which the mobile terminal is currently located or registered and neighboring cells, to determine whether to select another cell to camp on. Once a cell re-selection occurs, the network will receive a location update message from the mobile terminal and update the stored location information, (e.g., cell, location area, routing area, etc.), which may be used to page the mobile station.
Ideally, network operators would prefer to have total flexibility in directing or steering mobile subscribers between networks using different radio access technologies provided that the overlaying coverage exists, e.g., to divide the subscribers in different service categories like “gold/silver” subscriptions. This might mean that some mobile stations might camp on a UMTS-based cell while in an idle state as long as there is UMTS coverage. In contrast, mobile stations of subscribers having different subscription are directed to camp on a GSM/GPRS cell. These subscribers camping on GSM may still have the possibility to move to a UMTS cell when requesting certain services.
In order to provide satisfactory service to mobile subscribers and to maximize the capacity of a mobile communications network, it is important to balance the overall network load amongst the various cells within that network. It would be desirable to direct or steer mobile terminals from their respective current cells, if the loads in those current cells exceed a particular threshold, to an overlapping cell with a lower load. Switching active mobile stations with an active connection between cells requires substantial signaling, particularly when the switch is made from a cell in one radio access technology system to another, e.g., WCDMA to GSM. Moving active subscribers also requires that the connection between the mobile terminal and the network be maintained during the entire time that the intersystem change is taking place in order to ensure that the promised quality of service is maintained for that active connection. This consumes considerable resources in both the core and radio networks.
A better solution for satisfying subscriber preferences and network operator preferences, providing subscription services, and accomplishing network management type functions like load redistribution and many others is to dynamically distribute or “steer” in mobile stations to a particular cell or area. Multiple criteria are considered as compared to just considering only one criterion in terms of steering idle mobiles to a first service versus a second service area. In one non-limiting example implementation, the idle mobile stations are steered by adjusting a service area broadcast message parameter based on the multiple steering criteria. An offset may be applied to the broadcast parameter that either tends to steer idle mobile stations towards or away from the service area. For example, an offset parameter may be added to or subtracted from a signal that is measured by the mobile station for a service area selection procedure or a service area re-selection procedure. In order to avoid unnecessary battery drain in idle mobiles, the rate of change at which the broadcast message parameter is changed may be controlled.
Three idle mobile steering considerations are described in a non-limiting example. First, if roaming restrictions for certain service areas or a certain RAT apply to a mobile station, e.g., based on information stored in a mobile subscriber database like a home location register (HLR), the idle mobile station may be steered to an unrestricted service area. Such information might include subscriber information, service utilization history, etc. In one example implementation, roaming restrictions might receive a higher priority than other mobile steering criteria.
Second, knowledge in the network regarding overload conditions in certain service areas or RATs can be used to limit the registrations of incoming mobile stations. By rejecting registration requests to loaded service areas or a loaded RAT supported at a particular service area, mobile stations are re-directed to other less-loaded areas and/or RATs. This method acts as a relatively simple overload protection mechanism.
Third, actual load conditions are considered by the network, and idle mobiles may be steered by the network to balance the loads across multiple service areas or across different RATs. One or more parameters in cell broadcast messages may be adjusted in order to steer the mobile station to camp on a less loaded cell or other service area, or to use a less-loaded RAT. Thus, the cell-reselection procedures, usually driven by the quality of current radio conditions in particular cells, may be affected by adjusting one ore more broadcast parameters to effect a load balancing function.
The service areas may be cells, location areas, routing areas, service areas or the like. The adjustment may be initiated based upon load information from a core network node or from a radio access network node (e.g. from a central radio resource management server). In a preferred, non-limiting example application, a first service area is associated with a first mobile communications network that offers a first set of services, and a second service area is associated with the second mobile communications network that offers a second set of services. Of course, this methodology can be extended to third and additional communications networks, particularly when the subscribed services can be obtained from an additional network.
The first mobile communications network may employ a first radio access technology, and the second mobile communications network may employ a second different radio access technology. For example, the first mobile communications network may be a second generation-based network and the second communications network may be a third generation-based network. The first and second set of services may be different or the same.